I don't think that's a problem with LS, it's a bug with the file associations in the registry for firefox. I saw this somewhere the other day. I was having problems with firefox at work, but not at home, even though I was using the same theme, same OS, same version of firefox, etc. The problem is DDE related - look here for an explanation and a .reg file to fix it.

http://johnhaller.com/jh/mozilla/firefox_bug_246078.asp